1. Field of the Invention
Technology of electrical superconductors. Recently materials which have superconducting properties have been acquiring increasing importance. The discovery of new superconductor materials, in particular of the rare earths/Ba/Cu/O type led to an appreciable extension of the possible applications for superconductors since these substances become superconducting even at temperatures above 50 K.
The invention relates to the further development and improvement of components which contain a ceramic high-temperature superconductor in strip or wire form, it being intended to take the requirements of industrial large scale production into account.
In particular it relates to a conductor with an electrical conductivity of at least 0.85.times.10.sup.6 .OMEGA..sup.-1 cm.sup.-1 at 77 K composed of a composite material which is in turn composed of a conventionally conducting metallic part and a superconducting part.
2. Discussion of Background
Among the electrical conductors which exist as solids and are based on electron migration, two groups can essentially be distinguished: 1. the usual metallic conductors, such as copper, silver, aluminum etc. and their alloys, 2. the superconductors and, among them, specifically the ceramic sintered high-temperature superconductors based on oxides of the rare earth metals, of barium and of copper. The latter are very brittle and can, consequently, no longer be subjected to further shaping processes as a finished chemical compound. Their technology has been described in various publications (cf. for example, T. Kawai and M. Kanai, "Preparation of high-Tc Y--Ba--Cu--O Superconductor", Jap. Jour. of Applied Physics, Vol. 26, No. 5, May 1987, pages 2736-2737; Y. Yamada, N. Fukuschima, S. Nakayama and S. Murase, "Critical current density of wire type Y--Ba--Cu--Oxide superconductor", Jap. Jour of Applied Physics, Vol. 26, No. 5, May 1987, pages 2865-2866; H. Yoshino, N. Fukushima, M. Niu, S. Nakayama, Y. Amada and S. Murase, "Superconducting wire and coil with zero resistance state at 90 K and current density of 510 A/cm.sup.2 at 77 K", Toshiba Corporation, R + D Center, Saiwai-Ku, Kawasaki-City 210, Japan).
The unworkability of these compact high-temperature superconductor materials which exist as sintered bodies raises the question of new processing technologies, in particular in relation to an industrial manufacture of bodies in strip, sheet and wire form. There is a considerable need to extend the possible applications of such superconductors since they become superconducting even above 77 K (boiling point of nitrogen) and a complicated multistage refrigeration system using helium as the carrier medium becomes unnecessary.